Astronomy: Chapter 10 Flashcards
What is the observational evidence that some so-called “nebulae” are actually entire galaxies far outside our own galaxy?
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Describe the chief method for determining the masses of the galaxies, and what does this tell us about dark matter?
- Rotation Curve Method: Requires
- The true size of the orbits of stars or gas clouds within a galaxy, which in turn requires knowing the distance of that galaxy.
- the orbital speeds of the stars or gas clouds, measured from the doppler shifts of their spectral lines.
- Using keplers third law, we can find the mass of the part of the galaxy contained within the star orbit with measured size and speed.
- 95% of matter is dark matter.
Describe the factors involved in galactic formation, including the role of collisions between galaxies.
- Elliptical galaxies appear to be the product of galaxy mergers, which triggered star formation that used gas and dust.
- in the beginning, there were proto-galaxies. These proto-galaxies collided to create spiral galaxies. spiral galaxies collided to create elliptical galaxies.
- galaxies collide frequently. When they collide, gases compress with each other to form new gasses.
Be able to identify a galaxy by its shape, according to the Hubble telescope.
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Describe the observational evidence for the “dark matter” and discuss the most likely candidates for what it consists of.
The measured masses of galaxies amount to 10-100 times more mass than we can see. evidence indicates that there is 10-100 times more dark matter than visible matter in galaxies. Dark matter remains to be unresolved. Observations of galaxies and clusters of galaxies reveal that 90-95 percent of dark matter in the universe is dark matter.
State in your own words what the Hubble law really says and what its implications are concerning the expansion of the universe.
Hubble law: velocity of a galaxy is proportional to its distance.
Farther = faster.
Compare and contrast elliptical galaxies and spiral galaxies.
- Elliptical
- More common
- few young stars.
- most luminous stars are red giants.
- no blue giants.
- Red tint
- no visible gas or dust.
- Spiral
- spiral and flat
- smaller range of size.
- ancient red dwarf and blue giants
- hot bright stars, constantly luminous, easy to see.
- blue tint.
- contains gas and dust.
Describe the different types of active galaxies, and the mechanisms proposed to explain their energy output and other characteristics.
- Active galaxy: a galaxy whose center emits large amounts of excess energy, often in the form of radio emission. active galaxies have massive black holes in their centers into which matter is flowing.
- Radio Galaxy: a galaxy that is a strong source of radio waves.
- Seyfert Galaxies: an other wise normal spiral galaxy with an unusually bright, small core that fluctuates in brightness and a dim disk.
Briefly relate the story of the discovery of quasars.
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Discuss the controversy that originally surrounded quasars.
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Describe the current explanation of quasars and their energy sources.
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Briefly relate the story of the discovery of quasars.
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Discuss the controversy that originally surrounded quasars.
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Describe the current explanation of quasars and their energy sources.
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